uxon

My car is a '04 WRX. At the moment it is my allrounder - mostly driving around town and low quality B roads, sometimes highway.
Standard WRX suspension was a total disaster for me, it felt like a boat, very unconfident while spirited driving. The only positive with this set was that they were quite comfortable.
After that I mounted a set of STI takeoffs, more preciselly a set of Kayaba Ultra SR with standard sti v8 springs. This set is uncomparable to the previous one in terms how much confidence it provides. It is a big step further. But it has one huge drawback. I drive mainly on low quality roads with many pottholes and bumps and it is much too harsh/crashy in such conditions.
I would like to have something that makes car more planted but still confident for spirited driving. In general I am considering 3 options:
- Is there any solution to make STI suspension less harsh? Some specific set of springs for example? I have read that either Prodrive red (which are a bit harder) or Eibach Pro Kit (which are a bit softer) might be solution for the stock struts' harshness. Do you have any experience with that?
- The second option might be to reuse my stock WRX struts but with some better springs, for example Eibach Pro Kit. Do you think that used struts might work well with harder springs?
- The third option is a set of used coilovers. At the moment I could buy a second hand set of BC Racing or KWV1. But I read mixed opinions on them. Some say it's more comfortable than stock STI, others say it's totally opposite and cannot be driven anywhere but on a racetrack (which is something I am totally against).

2pot

iTrader: (3)

Assuming you've got inverted ultra sr? Change the front internal bump stops - the stock internal bump stops are 60mm long, rock-hard and used as a form of pitch control. They're too stiff for poor roads.

Avalyn

I've an 07 STi Hawkeye and have the same issue, and I'm primarily town, B-road too.


Next week I'm having the struts rebuilt/regreased and fitted a revised set of springs and front/rear bumpstops that I got from PCA dynamics in order to try and fix the issue.


I'm after less pitch/roll and bounce, but with a bit more compliance as at the moment it's the worst of both worlds - hard, crashy and bouncy.


I'll let you know how the car feels after the springs have bedded in. It may get traded if this doesn't sort it as it ruins the car for me.

plenty

iTrader: (13)

I have RB320 springs fitted to my widetrack and am pretty happy with them - they are compliant enough for everyday driving whilst being controlled enough for spirited driving on poor roads.

They were designed to be matched to custom Bilstein dampers however I have tested them with OE widetrack dampers and they work fine.

I haven't personally tested this but RB320 springs should also fit a narrowtrack OE sized perch. There's a new set on sale right now on the 'bay.

Another option would be the blue Prodrive WRX springs which are softer than STI and RB320 but far superior to OE WRX items for our conditions.These come up for sale used from time to time, and may be available new from PCA Dynamics.

As mentioned above, changing bump stops is essential.

If you do a search on this forum there's quite a lot of good info available on spring/damper combos for UK drivers - try searching for posts from 2pot, Modrich, InTurbo and myself.

TECHNOPUG

iTrader: (1)

OE WRX shocks with PCA springs. Or find a coilover that can be adjusted to WRX stiffness or less (Meister R?)

If your standard WRX suspnesion was tired, then it wasn't a true reflection of how a fresh set up works.

uxon

Valuable tip, I didn't know about it. But the other problem with stock suspention set is what's called bobble head on highway - and it is for sure not connected with bump stops.
About bump stops, can I just cut them in let's say 1/3? What about rears?


Take a look at this thread: https://www.scoobynet.com/1016983-bi...k-roads-5.html
TLDR: get a set of bilsteins and springs dedicated for RB320 version - of course if you could afford it
I am awaiting for your impression after installing your refreshened set. As far as I know PCA springs are clones of different versions of Prodrive springs. Could you ask PCA which exatly model did they sell to you? Are they just Prodrive red springs?

I have read somewhere, that rear bilstein RB320 dampers are of different shape that stock KYB, and since then rear springs are not interchangeable.
I have found many useful info about WRX suspension here (prodrive blue/PCA springs FTW, otherwise Eibachs), but not too much useful info about correcting the stock STI setup.

plenty

iTrader: (13)

Actually it is - the bump stop in the OE strut is the root cause of the bobble effect. Change the bump stop and the bobble goes away.

The rear RB320 springs work with OE STi KYB (widetrack) dampers. I'm running this setup right now. Here's a thread on the topic.

I've no reason to believe they wouldn't fit a narrowtrack damper as I believe the perch diameters are the same between widetrack and narrowtrack damper models (Bilstein excepted).

2pot

iTrader: (3)

The stock front bump stops do cause bobble-head.
There's very little bump (compression) travel, before you engage the front bump stop - hence bobble-head.

The red Prodrive 05-07 STI springs came with alternative front internal bump stops. The PCA WRX springs also come with the same alternative internal bump stops. The PCA blue springs were designed for wrx, not, sti dampers.
The rear internal bump stops are too soft. Changing to a shorter stiffer rear stop, means you can often reduce understeer enough, so avoiding a bigger rear bar.

The rb320 struts used 60mm 3-node soft bump stops front and rear and used increased compression damping instead.

uxon

It's interesting what you say about bump stops, but I am not fully convinced. That's why:
- on the highway, since road is in very good condition, suspension travels very little (it's the smallest amount of travel that I can really think of) - it shouldn't even touch the bump stops;
- the bobblehead in my opinion is connected mostly with rears (or at least I feel it this way, from back of the car);
- I have tried to search about "sti bump stops" and no one on the Internet talks about modifying stock sti bump stops (only in case when you change springs to shorter ones). I mean it's not a popular subject and it should be if it was a real reason behind the well known and infamous bobblehead effect.

Can I just cut one (the hardest) ring from the stock bump stops? Should this be a cure?

2pot

iTrader: (3)

The stock STI rides on its front bump stops, as a form of pitch control, under braking.

If you're feeling it from the rear, then the rear ride frequency is too high (rear too stiff, in relation to the front), then you get the sensation that your head-rest is constantly trying to nudge you in the back of the head. That sensation is speed dependent - might feel it at 50mph, but not at 70mph, or visa versa.

plenty

iTrader: (13)

The US forums have lots of info on this topic. See this thread and this thread, for example.

I have read reports of folks successfully trimming the stock bump stops, but IMO if you're going to the trouble of removing and disassembling your dampers (assuming you have the STi inverted damper) you'd might as well fit the smaller Prodrive items, which are available quite cheap from PCA.

2pot

iTrader: (3)

Or, in 3 months time, Eibach should have finished making the WA/A2 Blob/Hawk STI, dual-rate springs, for saloon and wagon:
Ground/closed top coils.
Linear from 15mm above ride height to coil bind.
RB320 front ride height + slightly higher spring rate - longer free-length to accommodate more struts (Koni inserts, non-inverted Ultra SR etc) .
Prodrive 05-07 sti rear ride height + 5mm
Matching front and rear bump stops for inverted and non-inverted struts.

uxon

Interesting.. Is it Eibach's product or yours manufactured by them (you have written some posts about your springs prototypes)?

I have read previously linked iwsti thread about sti bump stops/jounce bumpers and, indeed, there is a lot of useful information there. Unfortunatelly the thread is old (2007) and is dead now.
At the moment I wonder which setup would be better for crap-quality b-roads: only aftermarket bumpstops on stock sti springs, or altogether with red prodrive (or rb320) springs? Which setup will swallow bumps and potholes better?

One of the best Subaru setups ever, considering b-roads, was in P1, which spring rates were nearly identical to the standard STI GD spring rates. I have read that it also had improved bumpstops on all 4 corners. Maybe the bumpstops were the main difference between GD STI and GC P1? The dampers on P1 came from v6 STI which were red inverted Kayabas, very similiar to the ones in the GD STI - but do you know if they differ much in terms of valving/damper characteristics? The P1 struts/springs have opinion of being nearly critically dampened. On the other hand STI GD stock setup have opinion of being quite hardly overdamped. Maybe they are also nearly critically dampened for their springs, but not including very strong and too long bump stops?

plenty

iTrader: (13)

Changing bump stops alone will be a big improvement, but the Prodrive Red or RB320 springs is well worth doing additionally (and you’re going to the trouble of disassembling your suspension anyway so why not).

I have run the Prodrive springs and bump stops with OEM KYB dampers and have no complaints, albeit I tend to favour quite soft damper settings generally.

2pot

iTrader: (3)

My spring specs, made by Eibach.

The P1 springs were 194lb/in front, 157lb/in rear - Prodrive lowered the rates from the v5/6sti springs, to accommodate UK b-roads

The v6sti and P1 struts are the the same strut - the same bump stops and damping. Changing the front bump stops improves handling on uneven/undulating roads. Changing the rear stops means less understeer, without going to a bigger rear bar.

The Prodrive rb320 front springs are 12mm lower than the Prodrive sti front springs. The Prodrive STi springs are lower at the rear than the rb320.
You can see the front/rear ride height differences below


Prodrive red sti suspension


rb320 suspension

uxon

I appreciate your input, cheers guys.

I believe that you are talking about OEM KYB for the STI(red inverted struts), not for the WRX ? And the red Prodrive Springs, not the blue ones?
GD STI suspension has an opinion of being harsh (most people say it's because they are overdapmed). Have you felt much increase in comfort and stability on crap surfaces, when you switched from stock springs and bumpstops to the prodrive's versions?

The numbers you provided are in opposition to what can be found online: 215lb/in F, 195lb/in R. (vs 224/195 for v8 GD STI)
https://forums.nasioc.com/forums/showthread.php?t=31744
https://forums.nasioc.com/forums/sho....php?t=1744762
http://www.rs25.com/forums/f9/t19890...-my-wagon.html
https://mnsubaru.com/threads/spring-rate-chart.21596/
https://www.i-club.com/forums/suspen...g-rates-25083/

And finally I found this thread: http://www.rs25.com/forums/f9/t22651...ggestions.html where 2pot is describing his first hand experience with P1 springs. So I assume that all the info in the Internet about P1 springs is wrong? Isn't it possible that they were that soft when you measured them, because they were old, and they lost some of their firmness over the years?
If P1 springs, designed for bumpy roads, were that soft, than maybe stock GD STI springs are not too soft (as many say), but they are also too hard? 2pot, do you have any knowledge about the actual stiffness of the red prodrive and
the rb320 springs? Maybe they are also softer than stock sti springs (like P1 springs vs stock v6 sti)?

But the main qustion is: are the v6 and v8 sti struts the same? Or how much do they differ? Do you have any knowledge in the subject?
But won't changing rear bumpstops to harder ones have any negative influence on the ride quality/rear-end stability?
So RB320 has the shortest front suspension travel from all discussed versions. According to conclusions from the previously linked iwsti bumpstops thread, since front suspension has very short travel in stock form, the more travel left the better ride. And shortening front dampers' travel (by shorter springs) is the worst that you can do to your stock sti shocks. This is quite in the opposition to what prodrive did with the RB320.

2pot, haven't you received PM from me?

2pot

iTrader: (3)

I'm correct, on the P1 spring rates.

Your not giving enough influence to the gas pressure, or lack of, in the struts - which effects ride height and can add to the spring rate. With regard to the lower front ride height of the rb320 springs, re-read the last line of post #8

Yes, I know the spring rates of the rb320 and the Prodrive sti. Also, consider the pro's and con's of progressive or dual-rate springs.

Stiffer rear bump stops will re-balance an understeering chassis.

uxon

And, could you share the information with us? You provided info about the realistic P1 springs rates. Could you also provide the data for GD STI Prodrive springs ratios?
Also, do you know how much GD Sti inverted dampers differ from the previous versions inverted dumpers (including P1)?

I have PM'd you about bump stops mate, did you receive my message?

2pot

iTrader: (3)

Start extrapolating the info you've accumulated - I'll tell you if you're warm or cold

The bump stop kits match my spring specs, to the selected inverted/non-inverted dampers.

PCA dynamics should have the Prodrive bump stop set.

plenty

iTrader: (13)

Yes I was referring to springs designed for the STi, in response to your reference to the same (Prodrive Reds and RB320s). Neither of these springs is designed to be used with a WRX damper - the Prodrive/PCA "blue" springs are.

GD dampers are longer than GC ones. I believe GC dampers may fit but will lower your GD considerably. In terms of damping characteristics of the WRX or STi GD damper versus the GC8 v6 damper - no idea.

The shorter bump stop means that the RB320 actually has MORE travel on the spring before it hits the bump stop compared with the stock STi front end, despite the lower ride height. The stock STi basically sits on its bump stops most of the time.

2pot

iTrader: (3)

The rb320 and oem sti inverted both have a 60mm front stop.

The rb320 very soft front stop contributes next to nothing to the spring rate, under compression. Instead of the bump stop slowing down the bump travel, it's done by the compression damping of the strut.

uxon

According to mentioned iwsti thread, on stock springs front struts are about 10mm from hitting bump stops (empty car). Front rb320 springs are 30mm shorter and, as I have read, front bumpstops are 10mm shorter and much softer. So it seems that RB320 is sitting on front bump stops all the time, even when empty.

plenty, could you please refer to this question:


Nothing in life comes easy, ha? :P OK, I will play your game, at least a bit I will provide some statements, please refer to each of them. Here is the first one:
- General opinion that stock STI GD struts are overdamped is wrong. They are rather slightly oversprung for bumpy roads (especially including hard front bumpstops).

plenty

iTrader: (13)

Did already. Refer to post #4 on this thread. I can vouch that the Prodrive bump stop + spring combination is much better suited to bumpy roads than the OEM STi setup.

FYI - here is what Peter Cambridge (designer of Prodrive suspensions for GC and GD) had to say:

I can confirm the RB320 bump stop is 50mm long with a nice soft start. The KYB OEM front bump stop is 60mm long with a really firm initial rate.‎ This causes most of the bobbing ride of an STI and creates a lot of initial understeer on corner entry. You have to commit early with the throttle and use the front lsd to pull it round. This usually causes an initial increase in understeer which is unnerving. The RB320 bump stop allows the car to turn in naturally and when you get on the power it smoothly drags the car round. It's a faster and safer way to corner.

2pot

iTrader: (3)

OEM/KYB 60mm front stop.
Prodrive 50mm front stop, as provided with Prodrive's sti red springs.
The rb320 60mm stop is neither of these.


The Bilsteins I've opened, have all been a 60mm, 3-node, stop.

With my springs, I use differing 40mm front stops, for differing inverted dampers.

2pot

iTrader: (3)

Your questions are being answered; the clues are there.

Relatively, soft springs and relatively stiff damping - maximise the mechanical grip.

I prefer stiffer springs and smaller bars. But, the chosen damper will be life-limited, if asked to control too stiff a spring/bar combination. So, your spring choice may be restricted.
Personally, I prefer a linear rate, or as linear as you can make the spring, with the required free length (so the spring doesn't dislodge at full droop).

Unless we pay Peter Cambridge to re-design a Koni insert or a kyb damper, then we won't get close to squaring the circle, since the rb320 suspension was devised. Change the bump stops as a start.

A damper has low, medium and high speed damping. The 05-07 Prodrive sti spring may be 3-way progressive and 41N/mm 39N/mm.

plenty

iTrader: (13)

I've no reason to doubt your findings and myself have yet to open a Bilstein. However, I did check with Peter who confirmed that the 50mm bump stop (the lower one in the pic above) is used in the RB320 front struts.

Avalyn

This is what I received from Peter at PCA dynamics. 4 springs but not red/blue or black but I am guessing spring rates/lengths to a spec similar to the RB320?


Revised bumpstops front and rear, 50 cm and (hard to see) @ 75 cm by my crude measurements. I didn't remove from the packaging for a squeeze, but as I am totally ignorant what I have on just now (standard STi) I can't form any sort of opinion on comparison.


I was hoping to have these all fitted this week, but the guy I'm hoping to use has been on holidays and let me down twice now (not his fault) and I'm considering taking it down to RA motorsport in Perth if my current plan doesn't pan out.


Quite frankly the ride is doing my head in, and if I can't resolve it quickly now (I've had the car 3 months) it'll be getting traded in

2pot

iTrader: (3)

Make sure the fitters understand they're internal bump stops!
Otherwise you'll probably hear:
"Your springs are fitted, but we couldn't fit the bump stops, as they are the wrong size".

plenty

iTrader: (13)

I've not purchased springs from PCA, only bump stops, but presumably OP you requested RB320 spec and as they come with RB320 geo settings I've no doubt they are identical to RB320 items, only a different colour.

Make sure your mechanic installs the internal bump stops in the right orientation, and that they take the opportunity while the shocks are apart to re-grease the internals, to prevent future knocking issues.

You should experience a significant improvement once these are fitted - please post up your feedback!

Avalyn

Unfortunately my mechanic is due to go offshore for 4 weeks on Sunday, so it's going to be some time before I get the above fitted.


He's been on the Scooby scene since it began and has done a number of STi's. The first thing he said when I phoned was he'd recommend doing the nipple mod etc. so he's really clued up and I've faith he knows exactly what he's doing.


Peter sent me some special grease (you can see it in the pic, white stuff) he gets from Bilstein to regrease the internals.